The impact of kinetic effects on the properties of relativistic electron-positron shocks

TL;DR

This paper investigates how kinetic effects, especially non-thermal particles, influence the properties and structure of relativistic electron-positron shocks using a semi-kinetic approach based on particle-in-cell simulations.

Contribution

It introduces a semi-kinetic model that incorporates first-principles simulation data to refine MHD shock jump conditions and addresses magnetic field effects in Weibel-mediated shocks.

Findings

Upstream parameter variations significantly affect shock properties.

Deviations from standard MHD can reach up to 10%.

First quantitative definition of shock transition region.

Abstract

We assess the impact of non-thermally shock-accelerated particles on the magnetohydrodynamic (MHD) jump conditions of relativistic shocks. The adiabatic constant is calculated directly from first principle particle-in-cell simulation data, enabling a semi-kinetic approach to improve the standard fluid model and allowing for an identification of the key parameters that define the shock structure. We find that the evolving upstream parameters have a stronger impact than the corrections due to non-thermal particles. We find that the decrease of the upstream bulk speed yields deviations from the standard MHD model up to 10%. Furthermore, we obtain a quantitative definition of the shock transition region from our analysis. For Weibel-mediated shocks the inclusion of a magnetic field in the MHD conservation equations is addressed for the first time.